This invention relates to a process for alkylating an alkylatable isoparaffinic hydrocarbon with olefinic hydrocarbons. In another aspect, this invention relates to a process for the alkylation of isoparaffins with olefins in the presence of a hydrofluoric acid catalyst. In yet another aspect, this invention relates to an alkylation process wherein energy is conserved through the use of waste heat available in a stream obtained from the prefractionation zone. In still another aspect, this invention relates to an alkylation process wherein a side draw stream from the prefractionation zone is passed in indirect heat exchange relationship with the interheater of an isostripper. In another aspect, this invention relates to an alkylation process wherein the bottoms from the prefractionation zone is flashed prior to being charged to the isostripper thereby reducing the amount of liquid that needs to be heated and vaporized in the isostripper. In another aspect, this invention further relates to an alkylation process in which the majority of heat needed by an isostripper is supplied by a side draw stream taken from the prefractionation zone.
Alkylation of isoparaffinic hydorcarbons, such as isobutane, isopentane, and the like, with olefinic hydrocarbons such as propylene, butylene, amylenes, and the like is well known as a commercially important method for producing gasoline boiling range hydrocarbons. Generally, the alkylation of isoparaffins with olefins is accomplished by contacting the reactants with an acid-acting catalyst, settling the mixture to separate the catalyst from hydrocarbons, and further separating the hydrocarbon stream into its various components including the alkylate product. The alkylate is typically a mixture of isomers of heptane, octane, etc., with the exact composition depending upon the isoparaffin and olefin reactants used. Various types of catalysts have been utilized in this reaction, including sulfuric acid, hydrofluoric acid, phosphoric acid, certain halosulfonic acids, and aluminum chloride. The preferred catalyst is hydrofluoric acid, however, because of the relative ease with which it can be used and reused and because of the superior quality of the alkylate that is produced.
The energy requirements for heating the various separation zones and streams of an alkylation process are great and it would be desirable, therefore, to maintain the energy requirements of the alkylation process at a minimum level. This is particularly important where energy is valuable and the products for generating the energy are in relatively short supply and expensive.
Accordingly, it is an object of this invention to provide an improved alkylation process which conserves energy by utilizing the available heat in the process in a more efficient manner.
Another object of this invention is to provide an alkylation process which minimizes the energy requirements.
It is another object of this invention to provide an alkylation process wherein the majority of heat required by the isostripper is supplied by the waste heat available in a side draw stream from the prefractionation zone.
Another object of this invention is to provide an improved alkylation process in which the isostripper requires little, if any, additional heat energy than that obtained from an interheater which is heated by waste heat available in the process.
Other objects, aspects, and the several advantages of this invention will be apparent to those skilled in the art upon a study of the disclosure, the appended claims, and the drawing.